The present invention relates to a tool for magnetically locating and recovering an electric wire suspended within a hollow wall.
Electricians and the installers of electrical fixtures and telephones in houses and other structures often spend considerable time and effort in locating and retrieving an electrical conduit or wire which is suspended from above within a hollow wall and which is intended to be connected to an electrical outlet or other fixture to be located near the base of the wall.
In the past, the most commonly used method of locating the suspended wire involved cutting a small hole in the lower portion of the wall, inserting a hooked rod through the hole and attempting to snare and retrieve the electric wire through the hole. This method involves considerable guess work and error and is not easy to do even for an experienced electrician.
The use of magnetic force has been suggested to solve the problem of locating and recovering an electric wire hidden within a hollow wall. U.S. Pat. No. 3,078,073 shows a conductor holder which includes a magnet and a separate magnetically attractable sensor. U.S. Pat. No. 3,971,543 teaches a highly magnetizable sensor assembly which includes a chain to be attached to the end of the suspended electrical wire and a rod-shaped contactor at the other end of the chain and a separate housing member with a magnet on one end and a removable cap on its other end.
However, so far as I am aware, neither of the tools shown in U.S. Pat. Nos. 3,078,073 and 3,971,543 or any other tool utilizing magnetic force to locate and retrieve a hidden electrical wire has been available on the market.
I have invented a unique tool which utilizes magnetic force to first locate and then retrieve an electric conduit or wire which is suspended within a hollow wall. To utilize my tool a magnetically attractive weight preferably in the form of an iron ball is attached to the end of the electric wire before it is lowered down into the hollow wall.
My tool includes a powerful magnet preferably in the form of sphere surrounded by a shell or buoyant material such as cork or plastic foam suspended in a clear liquid such as water within a sealed transparent container made of non-conductive material. The weight of the magnet and its surrounding shell is equal to the weight of the liquid which it displaces, thus leaving the magnet free to float or move within the container in response to the magnetic attraction of nearby articles.
A rod-shaped handle of non-conductive material is attached to the container to be grasped in the hand to manipulate the container along the wall behind which the iron weight is hanging from the lower end of the electric wire to be located. As the container is moved directly opposite the suspended weight, the weight will tend to move toward the container and the magnet will float toward the hidden weight. Movement of the floating magnet within the liquid toward the side of the container pressed against the wall will, of course, be noted by the workman manipulating the container and thus he can mark with great accuracy the exact location of the end of the electric wire.
Having marked the location of the end of the electric wire, the tool also provides means to conveniently retrieve the end of the wire. To this purpose, a plurality of cylindrical magnets joined end to end by short lengths of chain are attached to the end of the handle. A small hole is then cut in the wall at the indicated location of the lower end of the wire. The cylindrical magnets attached to the handle are then pushed through the hole and the handle manipulated about until one of the magnets makes contact with the iron weight attached to the end of the electric wire. The magnets are then withdrawn through the hole together with the iron weight which is held against the magnet by magnetic force.
The electric wire is thus recovered for subsequent connection to the desired outlet or fixture.